The endocrine regulation of pituitary gonadotropin release will be investigated in adult pituitary-stalk-sectioned female rhesus macaques. The effects of chronic episodic infusions of gonadotropin-releasing hormone (GnRH) on serum gonadotropins will be used to assess the hypophyseal contribution to maintenance of cyclic ovarian activity. After gonadotropin secretion has been reestablished in ovariectomized animals, the feedback actions of gonadal steroids will be studied. Additional studies will be carried out in stalk-sectioned females with intact ovaries to determine if cyclic ovarian function can be reinstated in the absence of hypothalamic influence. Results of these studies will provide information on the sites of action of gonadal steroids. Chronic, episodic electrical stimulation of the ventral-medial-arcuate region of the hypothalamus in juvenile rhesus macaques will be used to elevate gonadotropin levels prematurely through the release of endogenous GnRH. If puberty is naturally initiated by the appearance of pulsatile GnRH secretion, we should be able to induce ovulatory cycles in female infants by mimicking this pulsatile secretion. These experiments will help us analyze the contribution of the pituitary to the control of ovulatory events and to determine if gonadal steroid action in the hypothalamus is necessary for cyclic ovarian function.